Heat a large skillet or Dutch oven over medium-high heat. Add the ground beef, chopped onion, green bell pepper, and minced garlic, then cook for 6–8 minutes while breaking up the beef until it is browned and the vegetables begin to soften.

Drain excess fat if necessary, leaving a small amount behind to carry the chili powder and cumin flavors. Stir in the undrained diced tomatoes, tomato sauce, water, chili powder, salt, and ground cumin.

Bring the tomato and beef mixture to a boil, stirring so the seasonings are evenly distributed. Add the uncooked elbow macaroni and stir until the pasta is coated in the liquid.

Reduce the heat to low, cover the skillet, and simmer for about 15 minutes. Stir several times during cooking so the macaroni cooks evenly and does not stick, keeping the pan covered between stirs.

Check the pasta for tenderness near the end of the simmering time. If the mixture becomes too dry before the macaroni is cooked, add a small amount of water and continue simmering.

Remove the skillet from the heat and sprinkle the shredded cheddar over the top. Cover for 1–2 minutes, or stir gently, until the cheese melts before serving.